多点光纤光栅测温系统在渗流监测中的应用研究

为了监测土石坝内的渗流水的情况,提出一种多点光纤Bragg 光栅传感器(FBG)的结构,采用InGaAs光电探测器阵列探测光强的光纤光栅传感阵列的波长解调方法。根据室内实验结果,对多点光纤光栅传感系统的可行性和监测数据的可靠性进行分析, 给出用于坝体温度场监测的光纤光栅传感器波长温度响应灵敏度可达到0.0091nm/℃。工程中采用电热脉冲方式对传感器附近小范围的土壤进行加热，使其与水的温度形成一定的温差，实测结果表明可以利用光纤光栅传感器监测温度异常的方法判断是否发生渗流, 从而实现对坝体内集中渗漏点的定位和自动监测。在系统防雷击、抗干扰性方面, 采用光纤光栅传感监测系统与传统仪器相比具有明显优势。

Application of multi-point optical fiber grating temperature measurement system on seepage monitoring

The structure of multi-point fiber Bragg grating (FBG) was adopted to monitor the situation of seepage in dam. It used the wavelength demodulation method which applied InGaAs photoelectric detector array to measure the light intensity. According to the laboratory data, possibility of the multi-point fiber grating sensor system and reliability of the measured data are analyzed. Results showed that the wavelength-temperature response sensitivity of the fiber grating sensor can reach 0.0091 nm/℃ of the temperature field in the dam. Engineering application showed that using the electric heat pulse method to heat the soil around sensors formed the temperature difference with the water, the actual measurement result showed that the method which uses fber grating to detect temperature difference can apply to monitor seepage. It can realize the positioning of concentrated seepage points in the dam and automatic monitoring. Compared with conventional instruments, the fiber grating sensing monitoring system has obvious advantages in resistance to thunderbolts and disturbances.